Multiple speed electrical hand power tool such as electric drill and the like

ABSTRACT

A motor provides power over an output shaft (8) to which is geared a multiple speed reduction gearing, which includes a planetary drive including planet gears (15) and a planet gear carrier (13). A main gear (6) with outer and inner gear teeth (10, 11) thereon is driven by the motor shaft (4) gear teeth (10, 11) thereon, which are engaged by planetary gears (15) located on a planetary gear carrier. An outer axially shiftable ring (20) is shiftable to either connect the outer gear teeth (10) to the output shaft (8) over the planetary gear carrier, or the planetary gear (15) to the carrier, the latter drive being either fixed, or through a slip engagement to provide for two speed, or continuously variable speed output from the drive motor.

[ Nov. 27, 1973 MULTIPLE SPEED ELECTRICAL HAND POWER TOOL SUCH ASELECTRIC DRILL AND THE LIKE Inventors; Dieter Stihnlein, Kaufering;Ewald Merz, Utting, both of Germany Assignee: Metabowerke KG., Closs,Ranch &

Schnitzler, Nurtingen, Germany Filed: Sept. 5, 1972 Appl. No.: 286,574

Foreign Application Priority Data Sept. 9, 1971 Germany P 21 45 009.9

US. Cl. 74/785 Int. Cl. F1611 3/48 Field of Search 74/785, 786, 787

References Cited UNITED STATES PATENTS 3,115,791 12/1963 Dean ..74/785XPrimary Examiner-Allan D. Herrmann Att0rneyRobert D. Flynn et a1.

[57 ABSTRACT A motor provides power over an output shaft (8) to which isgeared a multiple speed reduction gearing, which includes a planetarydrive including planet gears (15) and a planet gear carrier (13). A maingear (6) with outer and inner gear teeth (10, 11) thereon is driven bythe motor shaft (4) gear teeth (10, 11) thereon, which are engaged byplanetary gears (15) located on a planetary gear carrier. An outeraxially shiftable ring (20) is shiftable to either connect the outergear teeth (10) to the output shaft (8) over the planetary gear carrier,or the planetary gear (15) to the carrier, the latter drive being eitherfixed, or through a slip engagement to provide for two speed, orcontinuously variable speed output from the drive motor.

9 Claims, 4 Drawing Figures PATENTEURHVNIQIS 3774476 sum 1m 4PAIENIEDHUVZY 1915 3774.476

sum 3 0F 4 MULTIPLE SPEED ELECTRICAL HAND POWER TOOL SUCH AS ELECTRICDRILL AND THE LIKE The present invention relates to electric power toolsand more particularly to hand-held small electric drills and the likewhich have a variable speed output.

Electric power tools, such as electric drills, percussion tools, and thelike usually have a drive gear transmission which is geared to theoutput shaft or pinion of the motor. The gears used are customarily spurgears, worm drives, or the like. If the output shaft is .to provide morethan one speed, and the motor is essentially a single speed motor, thenit has been customary to so form the gear transmission that gear wheelscan be interchanged, or can be selectively engaged and disengaged inorder to provide for the desired transmission ratio. Such mechanicalengagement and disengagement of gears require an idler shaft for thegear change transmission, which is comparatively expensive to build andrequires additional space. To provide for reliable gear changing, aswell as for long life of the gears and low noise level, tolerances inmanufacture must be maintained with high accuracy. Hand-held power toolsshould be compact andsmall and the available space for the gearing isthus limited. The entire tool must be confined within a housing, theouter dimension of which is limited in order to permit ease of use.

It is an object of the present invention to provide an electric powertool, and more particularly a hand-held power tool which is soconstructed that a multiple speed transmission is incorporated therein,which requires but little space, which is simple to manufacture permitschange in speed within at least two ranges and which does not requirehigh accuracy in manufacture for a large number of relatively locatedparts.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, the output shaft of themotor is in driving engagement with a main gear which has coaxiallyarranged outer and inner gear teeth. A disk like planetary gear carrier,with at least one planetary gear thereon has a planetary gear in drivingengagement with the inner and the outer gear teeth of the main gear. Anaxially shiftable selector ring is selectively engageable with one ofthe gear teeth, preferably the outer ones of the main gear to lock theouter one of the main gear to the planetary gear carrier; the planetarygear carrier is locked to the output shaft of the power tool. If thering is shifted axially, engagement between the outer gear teeth and theplanetary gear carrier is broken, and the ring will then engagetheplanetary gear only. This ring can be locked to the housing, orconnected thereto by a slip coupling, so that the gearing ratio willthen be determined by the transmission ratio between the inner gear(which is in driving engagement by means of a pinion with the planetarygear) and the slip, if any, between the axially shiftable ring and thehousing.

The construction permits a substantial simplification of manufacturewith respect to the customary spur gears with an idler shaft since onlya single axial distance is critical namely between the output shaft ofthe motor and the output shaft from the power tool; in contrast, gearshaving idler shafts require close tolerances of three shaft distances.The power tool with the gearing can be located in a small space and canbe constructed with low weight, which is particularly important inhand-held power tools. Assembly and disassembly of the gearing, and ofthe tool as a whole is simple since the planetary gear carrier and theassociated shaft, which also forms the output shaft of the tool can beinserted as a single unit into the housing of the electric power tool;in case of replacement, it can be removed as a single unit. Theconstructional tolerances for the unit are comparatively wide and theseat and the arrangement of the axially shiftable ring also is notcritical and does not require small and accurately held relationships.This permits simple operation of the entire drive and ease of assemblyand disassembly.

If the axially shiftable ring is not positively locked, but is engagedby a fraction drive, for example over a brakeshoe, then the output speedof the tool can be controlled by slip, and in step-less variation. Inthis case the axially shiftable ring, rather than being locked is onlybraked to provide for controlled slip with respect thereto. By suitablebraking, that is, by suitable selection and control of the slip, it ispossible to control the speed of the output spindle in a continuouslyvariable mode.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 illustrates an axial cross-sectional view of the power tool withthe planetary gear drive;

FIG. 2 is a side view of planetary gear drive of the power tool of FIG.1

FIG. 3 is an axial cross-sectional view of the planetary gear drive ofthe power tool of FIG. 1; and

FIG. 4' is a transverse cross-sectional view along line III--III of FIG.3.

The housing 1 of the tool has a bearing 2 located therein in which theoutput shaft 3 from the motor M is rotatably journalled. This bearingmay, for example, be a roller bearing or a ball bearing and is onlyindicated schematically since the location and joumalling of outputshafts of electrically driven power tools are well known. The outputshaft has a pinion, or gearing 4 at the end thereof, which gearingengages matching gearing 5 of main gear 6. Main gear 6 is journalled ona shaft 8, which forms the output shaft of the power toolwhich isjournalled in a bearing 7, for example a sleeve bearing located withinthe housing 1 of the power tool. The main gear 6 provides rotationalpower to a planetary drive. To this end, one of the facing end sides,side 9, is formed with two coaxial gear teeth 10, 11. Gear teeth 10 arefacing outwardly and gear teeth 1 l are facing inwardly. In a simple wayof construction, the main gear 6 is formed as a gear cylinder to which aring 12, carrying the outer and inner gear teeth 10, 11 is secured, forexample by spot welding, riveting or the like, to form a secure andreliable interconnection between ring 12 and gear 6.

A planet gear carrier 13 is located on shaft 8 and keyed thereto, forexample by a key 14. Planet gear carrier 13 is placed immediatelyadjacent the main gear 6. Four planet gears 15 are located on theplanetary gear carrier 13 on the side facing the main gear 6, theplanetary gears 15 being journalled on shafts l6 and engaging a centralpinion 17, which is rotatable about shaft 8. Central pinion 17 is inconstant gearing engagement with the inner gearing ll of the gear ring12. Pinion 17 is thus in driving engagement with the main gear 6. Itfunctions, simultaneously, as a spacer between the planetary gearcarrier 13 and the main gear 6. The

main gear 6 is located on shaft 8 by a C-ring 18 bearing against awasher 19.

An axially shiftable gear change switching ring 20 surrounds theplanetary gear carrier 13. Switching ring 20 carries an inner gearing 21which is in constant engagement with the planetary gears 15. Upon axialshifting towards the left FIG. 3 the inner gearing 21 can be engagedwith the outer gear teeth 10 of the gear ring 12 secured to the maingear 6. Upon shifting to the right, driving engagement between ring 20and the main gear 6 is disconnected. The two possible positions of theswitching ring 20 are illustrated in FIG. 3, where the upper half (withrespect to the center line of shaft 8) indicates the position of ring 20when engaged with the gearing 10; the non-engaged position isillustrated in the lower half.

Switching ring 20 can be moved axially in a direction of arrow 31 by ashift knob 30 having a projection engaging in a groove 22 formed in ring20.

Ring 20 can be locked to the housing 1 or can be permitted to rotatewith respect thereto. A knob 35 is provided, secured to housing 1, forexample by being threaded therein. A brakeshoe 41 on a bolt 40 which isthreaded into the housing 1 is selectively engageable under pressureagainst the face of the ring 20. When the shiftknob 30 is shiftedtowards the right with respect to arrow 30, a projection 38 on knob 35forming a locking pin engages in lock holes 37 to positively lock thering 20.

Operation: Pinion 4, secured to the output shaft 3 of motor M is rotatedby the motor, and drives gear 6, thus rotating the gear ring 12. Gearring 12, in engagement with pinion 17, causes continuous rotation ofpinion 17 (see FIG. 4). If the ring 20 is in the left axial position theupper part of FIG. 3 then the inner gearing 21 of ring 20 is engagedwith the outer gear teeth 10 of gear ring 12. In effect, therefore, ring20 rotates together with the main gear 6. The planetary gears are lockedin position and cannot rotate with respect to their shafts 16.Therefore, the planetary gear carrier 13 rotates with the same speed asgear 6. Shaft 8, keyed by means of key 14 to the planetary gear carrier13 rotates likewise with the same speed as main gear 6.

If the switching ring is shifted to the right, as illustrated in thelower half of the center line of shaft 8 in FIG. 3, then the driveconnection between switching ring 20 and the main gear 6 is released.Planetary gears 15 now can rotate on the gearing of the pinion 17 and onthe inner teeth 21 of the ring 20. Since the planetary gear carrier 13is keyed to shaft 4, a step down gearing transmission will be effectedbetween the main gear 6 and the planetary gear carrier 13 due to thestep-down transmission provided by engagement of the inner gear teeth 11with the pinion 17 and the further connection between the pinion 17 andthe planetary gears 15 as they rotate about pinion 17. Ring 20, in thisposition, is fixed in space, for example by engagement of the projectionof the knob 35 within opening 37.

Alternatively, by first screwing knob 35 to the right (FIG. 1) and thentightening bolt 40 ring 20 can be brought in frictional engagement withthe brakeshoe 41, permitting, however, some slip. By suitable adjustmentof the slip, the speed of drive shaft 8 can be suitably controlled, in acontinuous and step-less manner.

Various changes and modifications may be made within the inventiveconcept; for example, the switching ring 20 need not be located at theouter circumference of the planetary gear carrier 13 so that it isengaged with the outer gear teeth 10 of the gear ring 12; rather, theswitching ring 20 could be formed as a central sleeve which is engagedwith the inner gear teeth 11 of the gear ring 12, and the function ofpinion 17 could be obtained by a gear ring having inwardly pro jectingteeth, similar to ring 20, and located in axial position.

The gear transmission is particularly suitable for small tools but canbe utilized for various apparatus in which space is at a premium, andassembly and disassembly must be rapid and simple and weight and costshould be held to a minimum.

We claim:

1. Electric multi-speed hand tool having a motor (M) and a motor outputshaft (3) providing motor output power;

a motor speed reduction gearing in driving engagement with the motoroutput shaft (3) comprising a main gear (6), in driving engagement withthe motor shaft and having coaxial outer (10) and inner (11) teeththereon;

a disk-like planetary gear carrier (13) having at least one planetarygear (15) located thereon; an outer, axially shiftable (31) ring (20)located coaxially to the main gear (6) and having gearing (21) thereonin continuous meshing engagement with the planetary gear (15), the ringbeing selectively engageable with one of the gear teeth (10, 11) of themain gear (6) in one axial position and disengaged therefrom in a secondaxial position;

and means (38, 41, 37) restraining rotation of the selectivelyengageable axially shiftable ring (20) when in the second axial positionwith respect to the planetary gear carrier (13).

2. Tool according to claim 1, wherein the rotation restraining meanscomprises a positive engagement lock.

3. Tool according to claim 1, wherein the rotation restraining meanscomprises a brakeshoe (41) permitting restrained, relative slip betweenthe planetary gear carrier (13 and the ring (20) to provide speedsintermediate the direct drive speed effected when the ring is in thefirst axial position and the low speed when the ring is in the secondaxial position.

4. Tool according to claim 1, wherein the main gear comprises a ringshaped element (6) having, at one face thereof (9), a gear ring (12)secured thereto, said gear ring carrying the inner and outer gear teeth(10,

and a spur gear (17) in meshing engagement with the inner gear teeth(11) and further in meshing engagement with the planetary gears (15).

5. Tool according to claim 4, wherein the spur gear (17) is a pinion andhas a length approximately equal to the sum of the axial length of theinner gear teeth (11) and of the planetary gear to provide a spacermember for the gear.

6. Tool according to claim 1, wherein the shiftable outer ring (20) isjoumalled on the planetary gear carrier (13) for rotary and axiallyshiftable movement with respect thereto.

7. Tool according to claim 1, further comprising an output shaft (8)joumalled in the tool, said output shaft being coupled to the planetarygear carrier (13) for rotation therewith, the main gear (6) beingrotatably main gear (6) being journalled on the output shaft forrotation with respect thereto and including a ringshaped element havingthe outer (l0) and inner (ll) gear teeth projecting from one face (9)thereof;

and a spur gear (17) joumalled on the output shaft and in engagementwith both the inner gear teeth (11) of the main gear and with theplanetary gears (15), so that, when the axially shiftable ring (20) isin the first axial position, the outer gear teeth (10) on the main gearand the planetary gears (15) will be locked together, the planetary gearcarrier (13) transmitting direct drive motion to the output shaft; andwhen the axially shiftable ring (20) is in the second axial position,the planetary gears (15) will be restrained with respect to theplanetary gear carrier (13) and rotation will be transmitted by theinner teeth (11) to the spur gear (17) and the output speed of theoutput shaft (8) will be determined by the gearing ratio of the innerteeth (11) and the spur gear, and of the spur gear (17) and theplanetary gears (15) and the degree of relative restraint between theplanetary gear carrier (13) and the shiftable ring (20).

1. Electric multi-speed hand tool having a motor (M) and a motor outputshaft (3) providing motor output power; a motor speed reduction gearingin driving engagement with the motor output shaft (3) comprising a maingear (6), in driving engagement with the motor shaft and having coaxialouter (10) and inner (11) teeth thereon; a disk-like planetary gearcarrier (13) having at least one planetary gear (15) located thereon; anouter, axially shiftable (31) ring (20) located coaxially to the maingear (6) and having gearing (21) thereon in continuous meshingengagement with the planetary gear (15), the ring being selectivelyengageable with one of the gear teeth (10, 11) of the main gear (6) inone axial position and disengaged therefrom in a second axial position;and means (38, 41, 37) restraining rotation of the selectivelyengageable axially shiftable ring (20) when in the second axial positionwith respect to the planetary gear carrier (13).
 2. Tool according toclaim 1, wherein the rotation restraining means comprises a positiveengagement lock.
 3. Tool according to claim 1, wherein the rotationrestraining means comprises a brakeshoe (41) permitting restrained,relative slip between the planetary gear carrier (13 and the ring (20)to provide speeds intermediate the direct drive speed effected when thering is in the first axial position and the low speed when the ring isin the second axial position.
 4. Tool according to claim 1, wherein themain gear comprises a ring shaped element (6) having, at one facethereof (9), a gear ring (12) secured thereto, said gear ring carryingthe inner and outer gear teeth (10, 11); and a spur gear (17) in meshingengagement with the inner gear teeth (11) and further in meshingengagement with the planetary gears (15).
 5. Tool according to claim 4,wherein the spur gear (17) is a pinion and has a length approximatelyequal to the sum of the axial length of the inner gear teeth (11) and ofthe planetary gear to provide a spacer member for the gear.
 6. Toolaccording to claim 1, wherein the shiftable outer ring (20) isjournalled on the planetary gear carrier (13) for rotary and axiallyshiftable movement with respect thereto.
 7. Tool according to claim 1,further comprising an output shaft (8) journalled in the tool, saidoutput shaft being coupled to the planetary gear carrier (13) forrotation therewith, the main gear (6) being rotatably journalled on theoutput shaft for rotation with respect thereto.
 8. Tool according toclaim 1, including a motor gear (4) on the output shaft of the motor (M)and gearing (4, 5) coupled to the main gear (6) and the motor gear; andan output shaft (8) journalled in the tool and in driven engagement withthe planetary gear carrier.
 9. Tool according to claim 1, comprising anoutput shaft (8) journalled in the tool and coupled (14) to theplanetary gear carrier (13) for rotation therewith, the main gear (6)being journalled on the output shaft for rotation with respect theretoand including a ring-shaped element having the outer (10) and inner (11)gear teeth projecting from one face (9) thereof; and a spur gear (17)journalled on the output shaft and in engagement with both the innergear teeth (11) of the main gear and with the planetary gears (15), sothat, when the axially shiftable ring (20) is in the first axialposition, the outer gear teeth (10) on the main gear and the planetarygears (15) will be locked together, the planetary gear carrier (13)transmitting direcT drive motion to the output shaft; and when theaxially shiftable ring (20) is in the second axial position, theplanetary gears (15) will be restrained with respect to the planetarygear carrier (13) and rotation will be transmitted by the inner teeth(11) to the spur gear (17) and the output speed of the output shaft (8)will be determined by the gearing ratio of the inner teeth (11) and thespur gear, and of the spur gear (17) and the planetary gears (15) andthe degree of relative restraint between the planetary gear carrier (13)and the shiftable ring (20).